An electronic lock for a safe deposit box generally comprises a key reading device, an electromagnetic opening device, and a bolt assembly. The key reading device is typically a password or fingerprint reading device, the electromagnetic opening device is primarily an electromagnet driven by an electromagnetic coil. The electromagnet is connected to and controlled by the key reading device. When the electromagnetic opening device is not powered on, the electromagnet extends out to block a bolt puling plate of the bolt assembly to prevent retraction of a spring bolt of the bolt assembly. After the key reading device has read a key and finished verification, the electromagnetic opening device will be energized to retract the electromagnet, and then an opening knob of the bolt assembly is rotated, thereby the bolt puling plate will drive the spring bolt to retract, and a door of the safe deposit box can be opened.
In general, in the electromagnetic opening device, a movable iron core is driven by an electromagnetic coil of an electromagnet, and a rebound spring structure is used to achieve locking and unlocking. Since a magnetism force of the electromagnet is limited and must be greater than an elastic force of a spring of the rebound spring structure, the elastic force of the spring shall not be too big. While if the elastic force of the spring is too small, in the event of shaking, knocking, shocking, etc., the movable iron core of the electromagnet may compress the spring under inertia effect of external force, thus invalidating a position-limit function against the bolt puling plate, and opening the safe deposit box abnormally, thereby greatly affecting stability and security of the safe deposit box.